1. Field of the Invention
The invention generally relates to the area of data communication and data storage and relates more particularly to low-density parity-check (LDPC) codes (LDPCCs) that support a plurality of rates while maintaining a constant block length.
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
LDPCCs are error-correcting codes used in data communications systems, as well as other systems like data storage devices. They were first introduced by Gallager in [1].
Practical data communication systems often need to operate at several different transmission rates. To keep the implementation as simple as possible, the same basic hardware architecture should be able to decode the encoded data at all the possible rates. One way to achieve this is to generate higher-rate codes by puncturing lower-rate codes. This technique was applied to convolutional codes in [2] and later applied to LDPC codes in [3] and [4]. However, puncturing reduces the code blocklength, which degrades performance. For the highest-rate codes where the puncturing is most severe, the performance degradation is significant when compared to an LDPCC with the original blocklength.
Another way to achieve this is to generate lower-rate codes by shortening higher-rate codes, as described in [4]. As with puncturing, shortening reduces the code blocklength, which degrades performance. For the lowest-rate codes where the shortening is most severe, the performance degradation is significant when compared to an LDPCC with the original blocklength.
The present invention describes a different approach that maintains the same blocklength across a plurality of rates.